Acute renal failure (ARF) has been the subject of increased attention. While comorbid factors affect patient outcome, the impact of nutrition, timing of initial support or acute dialytic dosing have not been adequately evaluated. Dialysis frequency has been derived from the stable End Stage Renal Failure population. Dialysis dosage measurements, which include patient-side surrogate marker (urea) toxin levels (Time averaged concentration-TACurea), marker substance removed (Solute removal Index (SRI), or the fractional clearance of urea for the dialysis session (Kwurea), have never been established in acute renal failure. While the ESRD Pt is at steady urea generation (G) and has a known urea space (V), the pt with ARF has large swings in G and enormous V variations. Also, the use of continuous hemodialytic modalities have not been subject to dosing evaluation. As a participant in an interactive Research Project Grant (IRPG), this study will establish a methodology describing dose delivery of either intermittent or continuous dialysis support to pts with ARF. The method will be used to investigate a possible link between delivered dialysis dose and pt outcome. All ICU pts with ARF requiring dialytic support will be targeted during the observational period (phase I). Demographic and comorbidity data will be gathered, and acuity scoring systems will classify each patient. Residual renal function (creatinine clearance or iothalamate clearance) will be measured. Dialysis support will be offered via ~customary~ prescription (with uniformed dialysis membrane and dialysate composition) as either intermittent hemodialysis (IHD) or continuous venovenous hemodialysis (CWHD). Each dialysis period will be described using urea by clearance-based (Kwurea derived from equilibrated urea kinetics), mass transfer-based (SRIurea derived from direct dialysate quantification (DDQ)), or resulting pt-based (TACurea) methodology. [Different collection techniques will be evaluated for direct dialysate quantification. Further a unified method of describing dialysis delivery based upon equivalent renal clearance [ekr] will be developed.] Gurea will be measured using normalized protein catabolic rates, while total body water (Vurea) will be measured using normalized protein catabolic rates, while total body water (Vurea) will be both calculated from DDQ and attempted to be measured by Bio-electrical impedance analysis (BIA) or DEXA scanning. [A final six month feasibility period will be utilized to establish the practicality, functionality and applicability of the unified mathematical algorithm used to monitor and readjust the dialysis prescription. Give a pre=determined aggressive eKRurea, compliance with the protocol, and impediments in achieving full implementation will be determined. It is expected that this project, along with the other IRPG generated data, will provide the building blocks for the design and implementation of future multi-centered interventional trials in Acute Renal Failure.]